Cellulosic biomass has recently attracted much attention as a renewable feedstock for chemicals and fuels. The industrially relevant compounds are typically produced via crude oil derived processes or by employing biotechnical approaches such as fermentation. One major challenge in the field is that the bio compounds are typically too oxygen-rich to be compatible with the current petroleum-based industry. The search for efficient deoxygenation methods has resulted a growing interest towards catalytic deoxydehydration (DODH) methods, in order to selectively convert bio-based resources into target chemicals.
In the prior art, Rennovia (WO 2010/144862 A2) describes a process for converting glucose to an adipic acid product via catalytic oxidation (glucose into glucaric acid) and catalytic hydrodeoxygenation (glucaric acid into adipic acid) by using hydrodeoxygenation catalyst together with a halogen source and H2.
Shiramizu and Toste (2013) describe a moderate conversion (43-94%) of mucic acid into adipic acid ester by using DODH and hydrogenation reaction. One of the downsides on muconic acid production according to Shiramizu and Toste is a remarkable stoichiometric sacrifice of the used 3-pentanol or 1-butanol (2-4 moles of alcohol spent per one mole of muconic acid product). Thus, one of the downsides on muconic acid production is a remarkable stoichiometric sacrifice of the used 3-pentanol or 1-butanol. For synthesis of muconic acid high temperatures are used (155° C.). Also the method uses fossil pentanol instead of renewable alcohol, such as methanol. In addition, pentanol as a reductant gives 4 molar equivalents of oxidized pentanol as a by-product.
Li et al. (2014) describe even more efficient conversion (up to 99%) of mucic acid into muconic acid through a DODH reaction, which is catalyzed by an oxorhenium complex. By combining DODH with transfer-hydrogenation reaction, mucic acid can be successfully converted into adipic acid. Li et al. use fossil pentanol and also an acid in addition to catalyst in their reactions. Shiramizu & Toste and Li et al. both describe the use of methyltrioxorhenium as a catalyst and 3-pentanol (or 1-butanol) as reductants, with reaction temperatures varying from 120° C. to 170° C.
Furan chemicals may also be produced via dehydroxylation of aldaric acids. However, current methods use strong mineral acids as reagents and reaction times are long, up to 40 hours (FR2723945, Taguchi et al., 2008).
Ahmad et al. (2011) describe production of olefins via sulfite-driven oxorhenium-catalyzed deoxydehydration of glycols. Solid reductant is used, which produces solid waste materials. Hydrogen is mentioned as an economically viable reductant, but this is only shown with THF. Ahmad et al. does not describe a method able to produce furans or muconic acids by using the same process set-up and only varying temperature.
As known, crude oil is a finite resource but essential. On the other hand, aldaric acids, such as galactric acid, can be produced from pectin and other non-edible carbohydrates. By converting aldaric acids to muconic acid and/or furans, a doorway is opened which allows for a wide variety of compounds to be prepared from bio-based resources, which would otherwise be prepared from crude oil stock. Thus, there is a need for a green method that avoids the use of finite resources and instead uses the advantageous techniques, utilizing organic synthesis and catalyst tools and allowing easy scalability, selectivity and ready purification of the desired chemicals.